Communication system



Jan. 3, 1939. C. J. FITCH COMMUNICATION SYSTEM Filed Aug. 51, 1935Patented Jan. 3, '1939 UNITED STATES PATENT OFFICE 2,142,351COMMUNICATION sirs'rEM` Clyde J. Fitch, Endicott, N. Y., assigner to1nternational Business Machines Corporation, New York, N. Y., acorporation of New York' Application August 31, 1935, Serial No. 38,698

1 Claim.

This invention relates to communication systems and more particularly toprinting telegraph systems and is suitably adaptable to both radio andwire network transmission.

The present invention will be explained in conjunction with a singleimpulse synchronous transmission system, in which the differentcharacters to be transmitted and received are repre- `by thetransformation of the waveshape of the signal during the progress of itstransmission or reception or both.

An object of this invention is to provide abbreviating means forcontrolling the time duration of the character pulse independently ofthe time duration of the impulse impressed on the input of the receivingsystem.

Another object of the present invention is to provide means foraccomplishing the abbreviation of the signal impulses by utilizing agaseous conduction device.

Various other objects and advantages of my invention will be obviousfrom the following particular description of one form of mechanismembodying the invention or from an inspection of the accompanyingdrawing; and the invention also constitutes certain new and novelfeaturesv of the construction and combination of parts hereinafter setforth and claimed.

In the drawing the circuits are shown which may be used in one preferredembodiment of the present invention.

It has been found that in synchronous systems of the type to bedescribed, namely, the single impulse system, the margins of operationat higher rates of transmission become quite limited. For such rates oftransmission, it is necessary to maintain exact synchroni'sm between thetransmitting and receiving distributors, and in addition thereto, totransmit and receive the character signals by extremely short impulses,so as to be positioned or allocated properly on the distributorsegments. However, it is well understood by those skilledv in the art,that transmission of signals either by radio or line networks under suchcritical conditions set forth numerous disadvantages, and prevent thehigher rates of transmission of character signals without utilizingcomplicated and elaborate correcting systems, which for commercialapplication and operation would be impractical.

It has been suggested to utilize a longer impulse for transmissionpurposes, and which is necessary for radio transmission due todistortion and mutilation of the signal Wave Shapes, and upon itsreception at the receiver, to suppress or abbreviate the signal so as toimpress but a part of it upon the respective distributor segments.

A system of this type is' disclosed in a copending application, SerialNo. 730,906, filed June 16, 1934, the principle of which appliedto theabove mentioned system renders faster possible rates of transmissionthan heretofore. The system just mentioned in the said application isbased on an electrical abbreviating system utilizing thermionic devicesadapted to trigger controlling electrostatic devices.

The present invention contemplates a similar treatment of the signalWave shapes, however, in

a more simple and cheaper manner, that is by utilizing gaseousconduction devices.

Inaccordance with the present invention a condenser having a slowcharging rate, is em. ployed in connection with a gaseous conductiondevice having a denite breakdown potential, the condenserbeing bridgedacross the gaseous conduction device so that after a predeterminedperiod of current flow the condenser accumulates a charge equal to thebreakdown potential of the gaseousl conduction ltube and dischargestherethrough, the discharge continuing until the charge is reduced tothe lower limit of the operating voltage of the tube, at which time thedischarge is discontinued abruptly.

It is the abbreviated impulse that is then applied or allocated on thecommutator segments of the distributor so as to permit faster rates ofoperation of the distributor and hence a greater rate of transmission ofintelligence.

It has mentioned hereinbefore that the particular type of communicationsystem explained in conjunction with the present invention is a printingtelegraph system operable by a line or radio network and involves theshifting of the character impulse along the axis of a timed scale, theposition of the impulse thereon deter-f mining the character to beselected, and is of the type disclosed in U. S. Patent No. 1,927,077,dated September 19, 1933.

Referring now to the drawing A represents a printing telegraph unitwhich may comprise any well known typewriter having a series ofcharacter pivoted key bars I0 and adapted to initiate a characterimpulse when one of the character keys is depressed.

The transmitting contacts may be positioned and associated directly withthe key bars as shown, wherein, a separate contact II is associated witheach individual key bar I0 and connected to the segments I2 of therotary distributor I3, a portion of the development of which is shown,and further disclosure thereof is deemed unnecessary since their use iswell known in the art. Rotary arm Il driven by any vsuitable means, suchas a motor, is adapted to engage the segments in rather rapid successionto cause the transmission of the character pulses.

One method of setting up the character signals is by the use ofcondensers and as shown an individual condenser I5 is associated witheach key bar Il), the said condensers connected by a common conductor toone side of a battery It.

It is to be noted that all the contacts iI, that/ is the normally closedcontacts, are associated with separate conducting segments I2 of thedistributor I3.

Disposed beneath and associated with the key bars I0 'and normally openare the contacts I1 and connected to one side of the condensers I5.These are provided so that when a character key is depressed theassociated condenser I5 normally charged will be discharged by shortingthe condenser through contact Il to ground.

supposing the key bar corresponding to character A is depressed todischarge its corresponding condenser, upon return of the key bar thecontact II is closed to connect the circuit from the battery I6 throughcondenser I5 and the closed contact II to its corresponding segmentI2--I, so that when the rotary arm I4 with its conducting brush engagescontact I, a circuit is completed through the solid conductor ring I8, yconductor I9 and the connected parallel circuit consisting of resistor20 and the primary winding of transformer 2|.`

Therefore, it is seen that upon completion of the circuit justdescribed, by the rotary arm I4 engaging the segment I2-I of thedistributor' the corresponding condenser conditioned upon depression ofthe A character key by its discharge, is now charged through theparallel circuit arrangement 20 and 2| to energize the secondary windingof the transformer and its connected circuit which may be a` wire orradio transmission network, utilizing transmitting equipment well knownin the art and need not be described herein in further detail. ,f-

The broad principle of operation of single impulse systems of the typereferred to, which is obvious, depends upon the synchronous operation ofthe distributing or rotary units associated with the respectivetransmitting and receiving units. Such synchronizing units are old andwell known to those skilled in the art, and therefore a detaileddescription of this unit is not necessary.

It is sufficient to mention that one type of synchronizing unit is suchutilizing periodic synchronizing impulse as, for example, asynchronizlng-impulse for each revolutionv of the transmitting rotarydistributor, and usually arranged so that if the rotary distributor atthe receiver lags as compared to the rotation of the transmittingdistributor, the receiving rotary brush, by virtue of such lagging,engages a contact segment to energize electroresponsive devices by thetransmitted synchronizing impulse to cause the rotary arm at thereceiver to be advanced to such an extent during its rotation so as totraverse the distributor segments in step with the transmittingdistributor. If the receiving rotary arm is leading the transmitting,engagement of another contact segment causes the electro-responsivedevices to retard the rotation of the rotary arm until synchronousoperation is attained. For a complete description of a synchronizingunit of the type just mentioned, reference may be made to the co-pendingapplication Serial No. 684,362, filed August 9, 1933.

A receiving distributor 25 similar to the transmitting distributor I3has disposed thereon the same number of segments 26 which are engaged insuccession by the brush attached to rotary arm 2l driven-by a suitablemotor or device so that the arms lll and 21 are rotated synchronously.

The aperiodically timed character signals are received in the well knownmanner by a receiver, generally designated, to energize the type barsolenoids 28 which are connected independently to the contact segments26 of the distributor. The circuit is completed by connecting the'commonterminals of the solenoids to the solid conducting ring 29. i

Interposed between the signal receiver and the distributor and recorderis a circuit embodying a gaseous conduction device 30.

The gaseous conduction device 30 may consist of a pair of opposedclosely spaced electrodes 3| and 32 contained within a sealed envelopefilled with one of the monatomic gases such as neon, argon or helium ormixtures thereof, the pressure of the gas and spacing of the electrodesbeing such that the device will have a definite starting or breakdownpotential.

It is a characteristic of negative glow tubes of this nature, when theelectrodes are thoroughly degasied and cleaned and pure gas employed, tohave an extremely uniform starting or breakdown potential over a longperiod of time, particularly when operated at .low current Adischarges,and after the discharge has been initiated therethrough, to continue toconduct current until the voltage has decreased considerably below thevalue required to start the'discharge.

The condenser 33 bridging the gaseous conduction device, graduallyassimilates a charge over an interval of time depending upon thecapacity of the. condenser and the value of the resistance 34, until itapproaches the Value of the breakdown potential of the tube 30.

When an additional charge is impressed on the condenser 33 due to areceived pulse impressed upon the circuit, the charge is such as toreach the breakdown potential of the tube 30. The condenser thendischarges through the tube and energizes the primary winding of thetransformers 35. The discharge continues until the voltage has decreasedto the lower limit of the operatlng voltage of the tube and is thenabruptly discontinued. The rate of discharge may be regulated by thevalue of the resistance 15a. In this manner the length of the impulsesimpressed on the contact segments 28 of the distributor can becontrolled to conform to various rates of operation of the system. It isunderstoodthat the length of the impulses can be varied by altering thecharacteristics of the circuit and that this pulse impressed on thesegments remains quite constant irrespective of the length of theimpulses impressed on the signal receiver.

In order to operate the described `system at 1| greater rates of speed,an abbreviator method of the type `disclosed comprising the gaseousconduction device and associated elements is highly desirable due to itssimplicity and eectiveness in increasing the operating margins of thesystem.

While there has been shown and described and pointed out the fundamentalnovel features of the invention as applied to a single modication, itwill be understood that various omissions and substitutions and changesin the form and details of the device illustrated and in its operationmay be made by those skilled in the art without departing from thespirit of the invention. It is the intention therefore to' be limitedonly as indicatedby the scope of the following claim.

What is claimed is:

A printing telegraph system comprising, in combination, means to receiveperiodic character signals, a printing telegraph recording unit, asignal control circuit connected to said receiving means includingserially a gaseous space discharge device, a first and second resistanceand a source of voltage, said source of voltage being below thebreak-down voltage of said device, a condenser connected in shunt ofsaid discharge device andthe rst said resistance and also in shunt ofthe source of voltage and the second resistance, said condenser arrangedto be charged relatively slowly through the said second resistance whencharacter signals are not impressed on said' circuit, and outlet circuitto said recording unit connected across said first resistance so thatupon reception of the character signals the said outlet circuit isenergized by the discharge of said device and condenser and the rst saidresistance controls the duration of the character signals sent over saidoutlet circuit, said outlet circuit inductively coupled to the receivingmeans in order that said signals may control the operation of therecording unit.

CLYDE J. FITCH.

CII

